The present invention relates to a nonhalogen flame-retardant polycarbonate composition comprising red phosphorous as a flame retardant. More particularly, the present invention relates to a nonhalogen flame-retardant polycarbonate composition comprising a polycarbonate resin, an acrylonitrile-butadiene-styrene terpolymer resin and red phosphorous.
Since high molecular plastics, especially engineering plastics, are known to have many advantages such as good physical properties, light-weight materials, low cost and easily processing, they have been gradually substituted for metals and widely utilized in, for example, electronic, mechanical, transportation, aeronautical engineering, biomedicine and architectural industries. Nevertheless, one of the major shortcomings of plastics is that they are easy to burn. Some plastics even produce large amounts of smoke during burning and are harmful to people and environment. Thus the flame-retardancy of plastics used in various industries is strictly provided. For instance, flammability test U.L. Subj. 94 is one test for the flame-retardancy of plastics.
To provide plastics with flame-retardancy, a traditional technique is to introduce halogen-containing flame-retardants in combination with flame-proofing additives such as Sb.sub.2 O.sub.3 into plastics. Most of such halogen-containing flame-retardants have diphenyl-oxide structures. Although such flame-retardants show significant flame-retardancy during burning, they simultaneously produce large amounts of fatal toxic smoke, i.e. Dioxin which is harmful to people. On the other hand, if polymers including halogen-containing flame-retardants are applied to the housings of monitors of office machines and electric appliances producing heat for long time such as television, dibenzofuran gases are produced and diffused. Therefore, the use of such polymers has been gradually prohibited around the world. For example, the European Community has gradually made laws to prohibit the use of halogen-containing flame-retardants. Since the relevant provisions are stricter than ever and the requirements on performance are upgraded, the high molecular plastics having high heat-resistance and good performance but having no halogen and smoke are required to meet the requirements for commercialized products, i.e. light, thin, short and small.
In recent years, heat stability and impact resistance were required in molding thermoplastic resins which have certain special uses. Therefore, the widely used plastics and ABS resins cannot satisfy these performance requirements. Instead, expensive heat-stable engineering plastics such as polycarbonates, polysulfones and polyphenyleneoxides were developed to solve these problems. Nevertheless, these high performance resins are not only expensive in cost but also are difficult to process. To improve processing properties and heat-resistance, the simplest way is to use polymer blending techniques. For example, ABS/PC polyblends have very balanced mechanical properties and processability. These polyblending techniques have been disclosed in Japanese Patent Application Nos. Sho 38-15225, 39-71 and 42-11496.
Since PC/ABS blends themselves do not have flame retardancy, they are not applicable to the products in electronic, information, mechanical and transportation industries. To improve the flame retardant characteristics of PC/ABS blends, the blends are traditionally admixed with halogen-containing retardants such as decarbromodiphenyl oxide in combination with Sb.sub.2 O.sub.3. However, such halogen-containing retardants generate large amounts of highly toxic smoke, dioxin. In order to avoid the environmentally harmful effects, plastic materials containing halogenated retardants have been gradually replaced by those containing nonhalogen retardants.
U.S. Pat. No. 4,692,488 discloses the use of phosphates such as triphenyl phosphate as halogen-free retardants for PC/ABS blends. Nevertheless, since the melting point of triphenyl phosphate is only 50.degree.-60.degree. C., if the amount added is large, plasticizing effect and migration phenomenon would occur and the distortion temperature of PC/ABS blends be greatly reduced. Under the circumstances, the field for application of such blends is limited.
Thereafter, General Electric Company in Japanese Laid-Open Application No. Hei 2-115262 discloses the use of arylphosphate monomers as non-halogen retardants for PC/ABS blends. Although the migration phenomenon is improved, these retardants cause a plasticizing effect on PC/ABS blends because the retardants per se are liquid. The high distortion temperature of PC/ABS blends is greatly reduced. The field for application of such retardants is also limited.
Accordingly, to overcome the above problems, the present invention provides a nonhalogen flame-retardant polycarbonate composition comprising a polycarbonate resin, an acrylonitrile-butadiene-styrene copolymer resin and red phosphorus. The composition according to the invention does not exhibit plasticizing effect or migration phenomenon and thus is quite suitable for use as a flame-retardant.